1. Field of the Invention
This invention relates to a friction mechanism for a lock-up clutch for a torque converter.
2. Description of the Related Art
Lock-up clutches of this type have been disclosed, e.g., in the following prior documents: U.S. Pat. No. 4,240,532; Japanese Examined Utility model Publication No. 61-28126; and Japanese Utility model application Nos. 61-170593 and 61-170594.
In such clutches, an input member and an output member, respectively, in the form of a piston and a driven plate, are circumferentially connected with each other by way of damper springs, or compressible coil springs, which absorb torque vibration.
Generally, such torque vibration in the clutch not only depends on the characteristic of the damper springs but also on the friction characteristic of the clutch. Therefore, the torsional vibration will be effectively absorbed when a friction member is arranged so as to generate a hysterisis torque corresponding to a relative movement between the piston and driven plate, or turbine wheel, of the torque converter.
However, such friction member has never been arranged in conventional lock-up clutch, because approximate hysterisis torque can not be determined.
As shown in FIG. 10. another conventional lock-up clutch 100 proposed for solving the above mentioned problem is known. I such lock-up clutch, clutch has an annular flange 103 installed between the turbine 101 and piston 102 and connected to turbine 101. A pair of side plates 104 and 105 are disposed at opposite sides of the flange 103. A friction member, consisting of a friction material 106 and a friction washer 107, is installed in at least one of the spaces formed between side plate 104 and the flange 103 and between flange 103 and side plate 105.
In such structure, the clutch 100 becomes complex because of the flange 103 and side plates 104 and 105. Thus, the cost of the clutch and total weight increases.